"His removal degrades ISIL's ability to conduct further attacks in the West and denies ISIL a veteran extremist with extensive ties," he added.

Hakim's death also "denies the Islamic State a key figure with extensive historical and current involvement in facilitation and external operations and degrades their ability to conduct terror attacks around the world," the statement read.

A US-backed Arab-Kurdish alliance on Saturday announced "phase two" of its campaign for Raqa, the IS group's Syrian bastion, as Washington said it was sending 200 more troops to back the offensive.

The battle for Raqa coincides with a vast US-backed offensive to retake Iraq's second city of Mosul from the jihadists.

Raqa and Mosul are the last major urban centers under IS control after the jihadists suffered a string of territorial losses in both countries over the past year.